It is conventional to apply sol-gel glasses onto ceramic substrates to form a liquid film of the sol which wets the surface of the ceramic. To cure the film to a ceramic coating, the film may then be exposed to an ammonia environment, to heat, or to both to gel the sol, and the gelled film may be fired at temperatures usually above 600.degree. F. to complete the coating. The ceramic substrates are generally insensitive and impervious to these firing temperatures. While this process is fine for ceramic materials, it cannot be used on sensitive materials where the sol and substrate are incompatible or where the substrate cannot tolerate high temperature firing. Certain metals, metal matrix composites, or metallized films will not be wetted by the sol, which will bead up rather than form a uniform liquid film. The method of the present invention allows protective ceramic coatings to be formed on these sensitive substrates, thereby extending their usefulness.